Why the apk application may not be installed on a smartphone?

Question

Android

I wrote a simple application with buttons that change color and inscription and created its apk in android studio.
I ran it on my Samsung, android studio emulator, xiaomi 7 genymotion emulator (7 android) - everything is fine.
A friend has a xiaomi redmi 5 smartphone with android 7 - the error "the application is not installed".
What are the criteria for the occurrence of this error in the android platform?

Answer 1

There are many criteria - the version of the axis, the version of something else in the manifest, free space, permission to install third-party applications, etc.
The easiest option is to either look at the logs in LogCat during installation, or install via ADB - there will be a readable error.

Answer 2

1) permission was not given to install applications not from Google Play;
2) when installing, the wrong items were selected;
3) do not fit according to Android version;
4) not enough memory.